One of the manifestations practiced, and promoted in the Toronto Blessing Movement, as well as in similar renewal and revival movements.
A person who is "doing the crunches" acts as if he or she is being punched in the stomach. He doubles over, and usually utters something like "oooh!" It is claimed to be an indication of the presence of the Holy Spirit, and proponents seriously see it as such.
There is no biblical justification for this phenomenon.